The Reasons and Treatment for Grape Yellow Leaves
The phenomenon of grape yellow leaves directly affects the quality and yield of the fruit, and is an important disease that troubles grape farmers. This article deeply analyzes the causes from three dimensions: soil improvement, light regulation, and nutrient supplementation, and provides operable solutions.
Soil Environment Improvement
Saline-Alkali Soil Management
When the soil pH value is greater than 7.5, the absorption of trace elements such as iron and zinc by grape roots is hindered, leading to typical chlorotic yellowing. Applying 50g of sulfur powder + 3kg of decomposed organic fertilizer per square meter can effectively reduce soil alkalinity, with a continuous regulation cycle of about 2-3 months.
Soil Hardening Repair
Deep tillage and loose soil need to be combined with bio-fertilizers. It is recommended to use the Y-shaped trenching method before spring sprouting, with a depth of 25-30cm, and apply the Bacillus subtilis preparation (10 billion CFU/g) at 2kg per mu, which can significantly improve the soil granular structure.
Light System Optimization
Leaf Pruning Standards
Using the 'Three-Zone Shaping Method' to retain the main stem zone, fruit zone, and ventilation zone, ensuring that the leaf area index per square meter is controlled between 1.8-2.2. Focus on pruning inner branches and crossed branches, maintaining a branch spacing of ≥15cm.
Supplementary Light Technology Application
It is recommended to install LED supplementary lights for facility cultivation, supplementing light for 4 hours daily (light intensity 2000-3000Lux), which can increase the chlorophyll content in leaves by over 25%. In open-field cultivation, the row spacing should be maintained at 2.5-3 meters, with a north-south planting orientation.
Precision Microelement Supplementation
Iron Deficiency Yellow Leaf Management
In addition to the underground bottle method (using 5% EDTA-Fe solution), it is recommended to spray chelated iron fertilizer (0.2% concentration) on the leaves, once a week for three consecutive weeks. Combined with the application of humic acid can increase the absorption efficiency of iron by 40%.
Nutritional Diagnosis and Prevention
Conduct leaf nutrient testing once each at the sprouting stage and after flowering every year, maintaining leaf iron content between 80-120mg/kg and zinc content between 20-30mg/kg. It is recommended to use slow-release medium and trace fertilizers (N-P2O5-K2O=8-12-15+TE) as a base application.
Through a three-dimensional governance system of soil improvement, light regulation, and nutrient management, combined with regular testing and preventive measures, the incidence of yellow leaf disease can be effectively controlled. It is recommended to establish an annual maintenance calendar, focusing on iron supplementation during the sprouting stage, strengthening drainage and preventing waterlogging during the rainy season, to achieve healthy and sustainable development of the grape garden.